[mdspan.submdspan.extents] Factor out common result expression

Author: tkoeppe

source/containers.tex

@@ -21817,20 +21817,17 @@
 \returns
 A value \tcode{ext} of type \tcode{SubExtents} such that
 for each $k$
-for which \tcode{\placeholder{map-rank}[$k$] != dynamic_extent} is \tcode{true}:
+for which \tcode{\placeholder{map-rank}[$k$] != dynamic_extent} is \tcode{true},
+\tcode{ext.extent(\placeholder{map-rank}[$k$])} equals:
 
 \begin{itemize}
 \item
-\tcode{ext.extent(\placeholder{map-rank}[$k$])} equals
-\tcode{$s_k$.extent == 0 ? 0 : 1 + (\exposid{de-ice}($s_k$.extent) - 1) /}\linebreak{}
-\tcode{\exposid{de-ice}($s_k$.stride)}
+\tcode{$s_k$.extent == 0 ? 0 : 1 + (\exposid{de-ice}($s_k$.extent) - 1) / \exposid{de-ice}($s_k$.stride)}
 if $S_k$ is a specialization of \tcode{strided_slice},
 
 \item
 otherwise,
-\tcode{ext.extent(\placeholder{map-rank}[$k$])} equals
-\tcode{\exposid{last_}<$k$>(src, slices...) -}
-\tcode{\exposid{first_}<Index-\linebreak{}Type, $k$>(slices...)}.
+\tcode{\exposid{last_}<$k$>(src, slices...) - \exposid{first_}<IndexType, $k$>(slices...)}.
 \end{itemize}
 \end{itemdescr}